Modern day consumers desire laundry detergents that provide excellent overall cleaning benefit with minimal environmental impact. The detergent industry has traditionally utilized surfactants to deliver the cleaning benefit. However, due to increasing environmental concerns, as well as rising costs of raw materials, the conventional way of either solely or heavily relying on surfactants to achieve the cleaning benefit is gradually losing favor with the modern day consumers.
Correspondingly, laundry detergent manufacturers are exploring new ways to reduce the amount of surfactants used in their products and to minimize the adverse impact of laundering on the environment, while still providing the consumer with excellent overall cleaning results.
Alkoxylated polyalkyleneimines are a group of polymers having a polyalkyleneimine backbone or core that is surrounded by polyalkylene oxide blocks. They have been used as detergent additives in low-surfactant detergent formulations to assist removal of soil from the fabric surface, stabilize suspension of soils dispersed in the wash liquor, and to prevent the suspended soil from redepositing back onto the fabric surface. For example, U.S. Pat. Nos. 8,097,579 and 8,247,268 disclose a group of water-soluble alkoxylated polyalkyleneimines that provide improved grease cleaning benefits, even at lower surfactant levels or at reduced temperatures. The use of such alkoxylated polyalkyleneimines enables reduction of the total surfactant level in laundry detergent products. Correspondingly, less surfactant is released into the environment after each wash, resulting in reduced environmental “footprint” of such laundry detergent products. Further, consumers will be able to accomplish the same cleaning benefit at lower washing temperature, e.g., using cold water, resulting in reduced carbon footprint of the laundering process.
Alkoxylated polyalkyleneimines have also been used as suds collapser to reduce the amount of water needed for rinsing off the laundry detergents after wash. Although high suds volume is desired during the wash cycle of laundering process to signal effective and sufficient cleaning, it is undesirable to have too much residue suds during the rinse cycle of laundering process because the residue suds signals to the consumer that there is still residue surfactant on the fabric and that additional rinsing is needed. Consequently, the consumer will keep rinsing the fabric until all the suds disappear, which inevitably leads to excessive water consumption. It is therefore desirable to use suds collapser, such as alkoxylated polyalkyleneimines, to help reduce or suppress suds during the rinse cycle. For example, U.S. Pat. No. 7,820,610 discloses the use of alkoxylated polyalkyleneimines as a suds collapser in laundry detergent formulations, which helps to reduce rinse suds and thereby prevent the consumer from using an excessive amount of water for rinsing. Correspondingly, the overall demand for water by the laundering process can be significantly reduced, which is an additional benefit that is particularly important for regions where water is a scarce resource.
It is clear that incorporation of alkoxylated polyalkyleneimines into laundry detergent products can effectively reduce the total amount of surfactants needed therein and minimize the adverse impact of laundering process on the environment, while still providing the consumer with excellent overall cleaning results.
However, alkoxylated polyalkyleneimines are viscous and therefore in the past they have been used mostly in liquid laundry detergent formulations. Although it is possible to try incorporating the alkoxylated polyalkyleneimines into dry powder or granular laundry detergent formulations by directly spraying a solution of such polymers onto already formed detergent granules containing surfactants and other detersive actives, the sprayed-on polymer may adversely affect the surface properties of the detergent granules, resulting in finished products with poorer flowability and higher tendency to “cake” over time.
There is therefore a need to provide alkoxylated polyalkyleneimines in a form that can be easily incorporated into granular or powder laundry detergent formulations with better flowability, reduced cake strength (i.e., lower tendency to “cake” over time) and overall product physical stability.